[WIP] Remove network.firewall.log-level field from configuration

[Copilot]

• Create pkg/cli/codemod_firewall_log_level.go - new codemod to remove log-level from network.firewall
• Create pkg/cli/codemod_firewall_log_level_test.go - tests for the new codemod
• Register new codemod in pkg/cli/fix_codemods.go
• Remove LogLevel field from FirewallConfig in pkg/workflow/firewall.go
• Simplify pkg/workflow/firewall_validation.go (remove ValidateLogLevel and log-level check)
• Remove log-level override in pkg/workflow/awf_helpers.go (always use default constant)
• Remove log-level extraction in pkg/workflow/frontmatter_extraction_security.go
• Remove log-level extraction in pkg/workflow/engine.go
• Remove log-level from pkg/parser/schemas/main_workflow_schema.json
• Delete pkg/workflow/firewall_log_level_test.go and update pkg/workflow/firewall_test.go
• Update pkg/cli/fix_codemods_test.go (count and order)
• Update docs: docs/src/content/docs/reference/network.md
• Update autocomplete: docs/public/editor/autocomplete-data.json
• Build and tests pass, code review clean

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